Currently, ships or sea vessels that are commercially utilized in the marine industry and U.S. Navy are propelled by waterjets discharged into the air above the water surface, and by propulsors that provide thrusting forces based on the rotation of propellers. The Navy is constantly searching for advanced technology to build high-speed ships. With the recent advance in hydrodynamic theories of ship resistance, hull form design methods and advanced propulsion technology, the Navy is developing high-speed ships with sprint/transient speeds of 38 to 45 knots. In the first phase of development, waterjet propulsion systems have been selected for high-speed ships.
Propeller drive systems are also being developed for high-speed ships. Typical surface ship propellers are limited to a maximum speed of 35 knots due to propeller cavitation and thrust breakdown. At full power, the ship speeds of most naval surface water vessels are in the order of 30 knots. However, propellers with advaced blade sections have been developed recently to achieve efficient operations at higher speeds. Twisted rudders have been successfully designed to avoid cavitation on the existing surface water vessels up to ship speeds of about 35 knots. At speeds above 35 knots, even twisted rudders may experience cavitation and erosion problems. The design technology of twisted rudders so successfully developed for existing surface water vessels that travel at speeds up to 35 knots, may not be adequate for speeds that exceed 35 knots. A rudder design for high-speed ships that avoids or reduces the effects of caviation and erosion is required.
Additionally, as opposed to waterjet propulsion system slipstreams, slipstreams produced by rotating propellers include rotational and tangential vectors. These vectors can be attributed to the rotational movement of the propellers. Consequently the rudders must also be designed to compensate for these variations in slipstream flow, particularly in high-speed environments.